1. Field of the Invention
The invention relates to a liquid discharging device for discharging liquid stored on a bottom wall of an interior of a compressed natural gas tank of a vehicle.
2. Description of the Related Art
In recent years, an engine of a vehicle using natural gas as fuel has been developed since an engine using natural gas generates less NO.sub.x and CO.sub.2 which cause a public hazard. For example, Japanese Unexamined Patent Publication No. 6-284821 discloses a compressed natural gas engine (CNG engine) which stores an amount of compressed natural gas in a compressed natural gas tank (CNG tank), extracts the compressed natural gas from the CNG tank, and reduces the pressure of the compressed natural gas by a regulator to use the natural gas as the fuel for the engine.
Water included in the natural gas is stored for a long time in the CNG tank which has a cylindrical central portion and opposed end portions connected to the central portion. Further, oil, from a compressor to the CNG tank when the compressor is activated to fill the CNG tank with the natural gas at high pressure, is mixed with the natural gas and is stored in the CNG tank. When the liquid such as water or oil included in the natural gas enters into the regulator, the liquid freezes due to the reduction in pressure of the natural gas by the regulator to cause damage to the regulator. At present, for the safety of the CNG tank, a liquid discharging opening for draining the water or oil cannot be provided in the bottom wall of the central portion of the CNG tank. Therefore, a complex operation of removing the CNG tank from the vehicle to discharge the liquid from the CNG tank is necessary.